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fastify-jwt

CI NPM version Known Vulnerabilities js-standard-style

JWT utils for Fastify, internally uses jsonwebtoken.

fastify-jwt supports Fastify@3. fastify-jwt v1.x supports both Fastify@2.

Install

npm i fastify-jwt --save

Usage

Register as a plugin. This will decorate your fastify instance with the standard jsonwebtoken methods decode, sign, and verify; refer to their documentation to find how to use the utilities. It will also register request.jwtVerify and reply.jwtSign. You must pass a secret when registering the plugin.

const fastify = require('fastify')()
fastify.register(require('fastify-jwt'), {
  secret: 'supersecret'
})

fastify.post('/signup', (req, reply) => {
  // some code
  const token = fastify.jwt.sign({ payload })
  reply.send({ token })
})

fastify.listen(3000, err => {
  if (err) throw err
})

For verifying & accessing the decoded token inside your services, you can use a global onRequest hook to define the verification process like so:

const fastify = require('fastify')()
fastify.register(require('fastify-jwt'), {
  secret: 'supersecret'
})

fastify.addHook("onRequest", async (request, reply) => {
  try {
    await request.jwtVerify()
  } catch (err) {
    reply.send(err)
  }
})

Afterwards, just use request.user in order to retrieve the user information:

module.exports = async function(fastify, opts) {
  fastify.get("/", async function(request, reply) {
    return request.user
  })
}

However, most of the time we want to protect only some of the routes in our application. To achieve this you can wrap your authentication logic into a plugin like

const fp = require("fastify-plugin")

module.exports = fp(async function(fastify, opts) {
  fastify.register(require("fastify-jwt"), {
    secret: "supersecret"
  })

  fastify.decorate("authenticate", async function(request, reply) {
    try {
      await request.jwtVerify()
    } catch (err) {
      reply.send(err)
    }
  })
})

Then use the preValidation of a route to protect it & access the user information inside:

module.exports = async function(fastify, opts) {
  fastify.get(
    "/",
    {
      preValidation: [fastify.authenticate]
    },
    async function(request, reply) {
      return request.user
    }
  )
}

Make sure that you also check fastify-auth plugin for composing more complex strategies.

Auth0 tokens verification

If you need to verify Auth0 issued HS256 or RS256 JWT tokens, you can use fastify-auth0-verify, which is based on top of this module.

API Spec

fastify-jwt

fastify-jwt is a Fastify plugin. You must pass a secret to the options parameter. The secret can be a primitive type String, a function that returns a String or an object { private, public }.

In this object { private, public } the private key is a string, buffer or object containing either the secret for HMAC algorithms or the PEM encoded private key for RSA and ECDSA. In case of a private key with passphrase an object { private: { key, passphrase }, public } can be used (based on crypto documentation), in this case be sure you pass the algorithm inside the signing options prefixed by the sign key of the plugin registering options).

In this object { private, public } the public key is a string or buffer containing either the secret for HMAC algorithms, or the PEM encoded public key for RSA and ECDSA.

Function based secret is supported by the request.jwtVerify() and reply.jwtSign() methods and is called with request, token, and callback parameters.

Example

const { readFileSync } = require('fs')
const path = require('path')
const fastify = require('fastify')()
const jwt = require('fastify-jwt')
// secret as a string
fastify.register(jwt, { secret: 'supersecret' })
// secret as a function with callback
fastify.register(jwt, {
  secret: function (request, token, callback) {
    // do something
    callback(null, 'supersecret')
  }
})
// secret as a function returning a promise
fastify.register(jwt, {
  secret: function (request, token) {
    return Promise.resolve('supersecret')
  }
})
// secret as an async function
fastify.register(jwt, {
  secret: async function (request, token) {
    return 'supersecret'
  }
})
// secret as an object of RSA keys (without passphrase)
// the files are loaded as strings
fastify.register(jwt, {
  secret: {
    private: readFileSync(`${path.join(__dirname, 'certs')}/private.key`, 'utf8'),
    public: readFileSync(`${path.join(__dirname, 'certs')}/public.key`, 'utf8')
  },
  sign: { algorithm: 'RS256' }
})
// secret as an object of P-256 ECDSA keys (with a passphrase)
// the files are loaded as buffers
fastify.register(jwt, {
  secret: {
    private: {
      key: readFileSync(`${path.join(__dirname, 'certs')}/private.pem`),
      passphrase: 'super secret passphrase'
    },
    public: readFileSync(`${path.join(__dirname, 'certs')}/public.pem`)
  },
  sign: { algorithm: 'ES256' }
})

Optionally you can define global default options that will be used by fastify-jwt API if you do not override them.

Additionally, it is also possible to reject tokens selectively (i.e. blacklisting) by providing the option trusted with the following signature: (request, decodedToken) => boolean|Promise<boolean>|SignPayloadType|Promise<SignPayloadType> where request is a FastifyRequest and decodedToken is the parsed (and verified) token information. Its result should be false or Promise<false> if the token should be rejected or, otherwise, be true or Promise<true> if the token should be accepted and, considering that request.user will be used after that, the return should be decodedToken itself.

Example

const { readFileSync } = require('fs')
const path = require('path')
const fastify = require('fastify')()
const jwt = require('fastify-jwt')
fastify.register(jwt, {
  secret: {
    private: readFileSync(`${path.join(__dirname, 'certs')}/private.pem`, 'utf8')
    public: readFileSync(`${path.join(__dirname, 'certs')}/public.pem`, 'utf8')
  },
  // Global default decoding method options
  decode: { complete: true },
  // Global default signing method options
  sign: {
    algorithm: 'ES256',
    issuer: 'api.example.tld'
  },
  // Global default verifying method options
  verify: { issuer: 'api.example.tld' }
})

fastify.get('/decode', async (request, reply) => {
  // We clone the global signing options before modifying them
  let altSignOptions = Object.assign({}, fastify.jwt.options.sign)
  altSignOptions.issuer = 'another.example.tld'

  // We generate a token using the default sign options
  const token = await reply.jwtSign({ foo: 'bar' })
  // We generate a token using overrided options
  const tokenAlt = await reply.jwtSign({ foo: 'bar' }, altSignOptions)

  // We decode the token using the default options
  const decodedToken = fastify.jwt.decode(token)

  // We decode the token using completely overided the default options
  const decodedTokenAlt = fastify.jwt.decode(tokenAlt, { complete: false })

  return { decodedToken, decodedTokenAlt }
  /**
   * Will return:
   *
   * {
   *   "decodedToken": {
   *     "header": {
   *       "alg": "ES256",
   *       "typ": "JWT"
   *     },
   *     "payload": {
   *       "foo": "bar",
   *       "iat": 1540305336
   *       "iss": "api.example.tld"
   *     },
   *     "signature": "gVf5bzROYB4nPgQC0nbJTWCiJ3Ya51cyuP-N50cidYo"
   *   },
   *   decodedTokenAlt: {
   *     "foo": "bar",
   *     "iat": 1540305337
   *     "iss": "another.example.tld"
   *   },
   * }
   */
})

fastify.listen(3000, err => {
  if (err) throw err
})

Example using cookie

In some situations you may want to store a token in a cookie. This allows you to drastically reduce the attack surface of XSS on your web app with the httpOnly and secure flags. Cookies can be susceptible to CSRF. You can mitigate this by either setting the sameSite flag to strict, or by using a CSRF library such as fastify-csrf.

Note: This plugin will look for a decorated request with the cookies property. fastify-cookie supports this feature, and therefore you should use it when using the cookie feature. The plugin will fallback to looking for the token in the authorization header if either of the following happens (even if the cookie option is enabled):

  • The request has both the authorization and cookie header
  • Cookie is empty, authorization header is present
const fastify = require('fastify')()
const jwt = require('fastify-jwt')

fastify.register(jwt, {
  secret: 'foobar'
  cookie: {
    cookieName: 'token'
  }
})

fastify
  .register(require('fastify-cookie'))

fastify.get('/cookies', async (request, reply) => {
  const token = await reply.jwtSign({
    name: 'foo',
    role: ['admin', 'spy']
  })

  reply
    .setCookie('token', token, {
      domain: 'your.domain',
      path: '/',
      secure: true, // send cookie over HTTPS only
      httpOnly: true,
      sameSite: true // alternative CSRF protection
    })
    .code(200)
    .send('Cookie sent')
})

fastify.addHook('onRequest', (request) => request.jwtVerify())

fastify.get('/verifycookie', (request, reply) => {
  reply.send({ code: 'OK', message: 'it works!' })
})

fastify.listen(3000, err => {
  if (err) throw err
})

Example trusted tokens

const fastify = require('fastify')()

fastify.register(require('fastify-jwt'), {
  secret: 'foobar',
  trusted: validateToken
})

fastify.addHook('onRequest', (request) => request.jwtVerify())

fastify.get('/', (request, reply) => {
  reply.send({ code: 'OK', message: 'it works!' })
})

fastify.listen(3000, (err) => {
  if (err) {
    throw err
  }
})

// ideally this function would do a query against some sort of storage to determine its outcome
async function validateToken(request, decodedToken) {
  const denylist = ['token1', 'token2']

  return !denylist.includes(decodedToken.jti)
}

Example with formatted user

You may customize the request.user object setting a custom sync function as parameter:

const fastify = require('fastify')();
fastify.register(require('fastify-jwt'), {
  formatUser: function (user) {
    return {
      departmentName: user.department_name
      name: user.name
    }
  },
  secret: 'supersecret'
});

fastify.addHook('onRequest', (request, reply) =>  request.jwtVerify());

fastify.get("/", async (request, reply) => {
  return `Hello, ${request.user.name} from ${request.user.departmentName}.`;
});

fastify.jwt.sign(payload [,options] [,callback])

The sign method is an implementation of jsonwebtoken .sign(). Can be used asynchronously by passing a callback function; synchronously without a callback.

fastify.jwt.verify(token, [,options] [,callback])

The verify method is an implementation of jsonwebtoken .verify(). Can be used asynchronously by passing a callback function; synchronously without a callback.

Example

const token = fastify.jwt.sign({ foo: 'bar' })
// synchronously
const decoded = fastify.jwt.verify(token)
// asycnhronously
fastify.jwt.verify(token, (err, decoded) => {
  if (err) fastify.log.error(err)
  fastify.log.info(`Token verified. Foo is ${decoded.foo}`)
})

fastify.jwt.decode(token [,options])

The decode method is an implementation of jsonwebtoken .decode(). Can only be used synchronously.

Example

const token = fastify.jwt.sign({ foo: 'bar' })
const decoded = fastify.jwt.decode(token)
fastify.log.info(`Decoded JWT: ${decoded}`)

fastify.jwt.options

For your convenience, the decode, sign, verify and messages options you specify during .register are made available via fastify.jwt.options that will return an object { decode, sign, verify, messages } containing your options.

Example

const { readFileSync } = require('fs')
const path = require('path')
const fastify = require('fastify')()
const jwt = require('fastify-jwt')
fastify.register(jwt, {
  secret: {
    private: readFileSync(`${path.join(__dirname, 'certs')}/private.key`),
    public: readFileSync(`${path.join(__dirname, 'certs')}/public.key`)
  },
  sign: {
    algorithm: 'RS256',
    audience: 'foo',
    issuer: 'example.tld'
  },
  verify: {
    audience: 'foo',
    issuer: 'example.tld',
  }
})

fastify.get('/', (request, reply) => {
  const globalOptions = fastify.jwt.options

  // We recommend that you clone the options like this when you need to mutate them
  // modifiedVerifyOptions = { audience: 'foo', issuer: 'example.tld' }
  let modifiedVerifyOptions = Object.assign({}, fastify.jwt.options.verify)
  modifiedVerifyOptions.audience = 'bar'
  modifiedVerifyOptions.subject = 'test'

  return { globalOptions, modifiedVerifyOptions }
  /**
   * Will return :
   * {
   *   globalOptions: {
   *     decode: {},
   *     sign: {
   *       algorithm: 'RS256',
   *       audience: 'foo',
   *       issuer: 'example.tld'
   *     },
   *     verify: {
   *       audience: 'foo',
   *       issuer: 'example.tld'
   *     }
   *   },
   *   modifiedVerifyOptions: {
   *     audience: 'bar',
   *     issuer: 'example.tld',
   *     subject: 'test'
   *   }
   * }
   */
})

fastify.listen(3000, err => {
  if (err) throw err
})

decode options

  • json: force JSON.parse on the payload even if the header doesn't contain "typ":"JWT".
  • complete: return an object with the decoded payload and header.

sign options

  • algorithm (default: HS256)
  • expiresIn: expressed in seconds or a string describing a time span zeit/ms. E.g.: 60, "2 days", "10h", "7d". A numeric value is interpreted as a seconds count. If you use a string be sure you provide the time units (days, hours, etc.), otherwise milliseconds unit is used by default ("120" is equal to "120ms").
  • notBefore: expressed in seconds or a string describing a time span zeit/ms. E.g.: 60, "2 days", "10h", "7d". A numeric value is interpreted as a seconds count. If you use a string be sure you provide the time units (days, hours, etc.), otherwise milliseconds unit is used by default ("120" is equal to "120ms").
  • audience
  • issuer
  • jwtid
  • subject
  • noTimestamp
  • header
  • keyid
  • mutatePayload: if true, the sign function will modify the payload object directly. This is useful if you need a raw reference to the payload after claims have been applied to it but before it has been encoded into a token.

verify options

  • algorithms: List of strings with the names of the allowed algorithms. For instance, ["HS256", "HS384"].
  • audience: if you want to check audience (aud), provide a value here. The audience can be checked against a string, a regular expression or a list of strings and/or regular expressions. E.g.: "urn:foo", /urn:f[o]{2}/, [/urn:f[o]{2}/, "urn:bar"]
  • issuer (optional): string or array of strings of valid values for the iss field.
  • ignoreExpiration: if true do not validate the expiration of the token.
  • ignoreNotBefore...
  • subject: if you want to check subject (sub), provide a value here
  • clockTolerance: number of seconds to tolerate when checking the nbf and exp claims, to deal with small clock differences among different servers
  • maxAge: the maximum allowed age for tokens to still be valid. It is expressed in seconds or a string describing a time span zeit/ms. E.g.: 1000, "2 days", "10h", "7d". A numeric value is interpreted as a seconds count. If you use a string be sure you provide the time units (days, hours, etc.), otherwise milliseconds unit is used by default ("120" is equal to "120ms").
  • clockTimestamp: the time in seconds that should be used as the current time for all necessary comparisons.
  • extractToken(request): token: Callback function allowing to use custom logic to extract the JWT token from the request.

messages options

For your convenience, you can override the default HTTP response messages sent when an unauthorized or bad request error occurs. You can choose the specific messages to override and the rest will fallback to the default messages. The object must be in the format specified in the example below.

Example

const fastify = require('fastify')

const myCustomMessages = {
  badRequestErrorMessage: 'Format is Authorization: Bearer [token]',
  noAuthorizationInHeaderMessage: 'Autorization header is missing!',
  authorizationTokenExpiredMessage: 'Authorization token expired',
  // for the below message you can pass a sync function that must return a string as shown or a string
  authorizationTokenInvalid: (err) => {
    return `Authorization token is invalid: ${err.message}`
  }
}

fastify.register(require('fastify-jwt'), {
  secret: 'supersecret',
  messages: myCustomMessages
})

fastify.jwt.secret

For your convenience, the secret you specify during .register is made available via fastify.jwt.secret. request.jwtVerify() and reply.jwtSign() will wrap non-function secrets in a callback function. request.jwtVerify() and reply.jwtSign() use an asynchronous waterfall method to retrieve your secret. It's recommended that your use these methods if your secret method is asynchronous.

fastify.jwt.cookie

For your convenience, request.jwtVerify() will look for the token in the cookies property of the decorated request. You must specify cookieName. Refer to the cookie example to see sample usage and important caveats.

reply.jwtSign(payload, [options,] callback)

request.jwtVerify([options,] callback)

These methods are very similar to their standard jsonwebtoken counterparts.

Example

const fastify = require('fastify')()
const jwt = require('fastify-jwt')
const request = require('request')

fastify.register(jwt, {
  secret: function (request, reply, callback) {
    // do something
    callback(null, 'supersecret')
  }
})

fastify.post('/sign', function (request, reply) {
  reply.jwtSign(request.body.payload, function (err, token) {
    return reply.send(err || { 'token': token })
  })
})

fastify.get('/verify', function (request, reply) {
  request.jwtVerify(function (err, decoded) {
    return reply.send(err || decoded)
  })
})

fastify.listen(3000, function (err) {
  if (err) fastify.log.error(err)
  fastify.log.info(`Server live on port: ${fastify.server.address().port}`)

  // sign payload and get JWT
  request({
    method: 'POST',
    headers: {
      'Content-Type': 'application/json'
    },
    body: {
      payload: {
        foo: 'bar'
      }
    },
    uri: `http://localhost:${fastify.server.address().port}/sign`,
    json: true
  }, function (err, response, body) {
    if (err) fastify.log.error(err)
    fastify.log.info(`JWT token is ${body.token}`)

    // verify JWT
    request({
      method: 'GET',
      headers: {
        'Content-Type': 'application/json',
        authorization: 'Bearer ' + body.token
      },
      uri: 'http://localhost:' + fastify.server.address().port + '/verify',
      json: true
    }, function (err, response, body) {
      if (err) fastify.log.error(err)
      fastify.log.info(`JWT verified. Foo is ${body.foo}`)
    })
  })
})

Verifying with JWKS

The following example integrates the get-jwks package to fetch a JWKS and verify a JWT against a valid public JWK.

Example

const Fastify = require('fastify')
const fjwt = require('fastify-jwt')
const buildGetJwks = require('get-jwks')

const fastify = Fastify()
const getJwks = buildGetJwks()

fastify.register(fjwt, {
  decode: { complete: true },
  secret: (request, token) => {
    const { header: { kid, alg }, payload: { iss } } = token
    return getJwks.getPublicKey({ kid, domain: iss, alg })
  }
})

fastify.addHook('onRequest', async (request, reply) => {
  try {
    await request.jwtVerify()
  } catch (err) {
    reply.send(err)
  }
})

fastify.listen(3000)

Algorithms supported

The following algorithms are currently supported by jsonwebtoken that is internally used by fastify-jwt.

algorithm(s) Parameter Value Digital Signature or MAC Algorithm
HS256 HMAC using SHA-256 hash algorithm
HS384 HMAC using SHA-384 hash algorithm
HS512 HMAC using SHA-512 hash algorithm
RS256 RSASSA using SHA-256 hash algorithm
RS384 RSASSA using SHA-384 hash algorithm
RS512 RSASSA using SHA-512 hash algorithm
ES256 ECDSA using P-256 curve and SHA-256 hash algorithm
ES384 ECDSA using P-384 curve and SHA-384 hash algorithm
ES512 ECDSA using P-521 curve and SHA-512 hash algorithm
none No digital signature or MAC value included

TypeScript

This plugin has two available exports, the default plugin function fastifyJwt and the plugin options object FastifyJWTOptions.

Import them like so:

import fastifyJwt, { FastifyJWTOptions } from 'fastify-jwt'

Define custom Payload Type

typescript declaration merging

declare module "fastify-jwt" {
  interface FastifyJWT {
    payload: { name: string }
  }
}

fastify.get('/', async (request, replay) => {
  request.user.name // string

  const token = await replay.jwtSign({
    name: 123
    // ^ Type 'number' is not assignable to type 'string'.
  });
})

Acknowledgements

This project is kindly sponsored by:

License

Licensed under MIT.